US8037704B2

US8037704B2 - Distributed refrigeration system

Info

Publication number: US8037704B2
Application number: US12/125,097
Authority: US
Inventors: Herman H. Viegas
Original assignee: Thermo King Corp
Current assignee: Thermo King LLC
Priority date: 2008-05-22
Filing date: 2008-05-22
Publication date: 2011-10-18
Also published as: WO2009142838A2; DE102009021442B4; CN101585336A; US20090288438A1; WO2009142838A3; CN101585336B; DE102009021442A1; GB2460146B; GB0906924D0; GB2460146A

Abstract

A refrigeration system configured for use with a trailer including a container having a roof, a first sidewall, and a second sidewall. The refrigeration system includes a refrigeration unit configured to couple to the trailer and operable to condition the container. The refrigeration system also includes a duct in fluid communication between the refrigeration unit and an opening in the first sidewall. The duct is configured to direct an airflow in at least one of a first direction toward the refrigeration unit and a second direction away from the refrigeration unit.

Description

BACKGROUND

The present invention relates to refrigeration systems. More particularly, the present invention relates to distributed refrigeration systems for trailers.

Large trucks (e.g., semi-tractor trailers) are commonly used to store and transport cargo, such as food product, within a trailer at a reduced or refrigerated temperature. Typically, the trailer includes a refrigeration system to maintain the cargo at the reduced temperature. One common type of refrigeration system includes a refrigeration unit having a compressor directly driven by a diesel engine and belt-driven condenser and evaporator fans. Another common type of refrigeration system includes a refrigeration unit that is electrically driven by an alternator coupled to the engine.

In either scenario, a single refrigeration unit is generally located on a front wall of a container of the trailer. The refrigeration unit typically must provide cooling to the entire container, even though some containers may be up to fifty-three feet long in trailers and seventy-two feet long in rail cars. As such, a powerful air circulation system is required to maintain a uniform temperature throughout the trailer. However, the energy required to operate the air circulation system and move air from one end of the container to another substantially reduces the overall efficiency of the refrigeration system.

In addition, if the container includes multiple compartments or portions that should be cooled to different temperatures, the complexity of the refrigeration system is greatly increased. For example, lengthy piping and additional flow control valves are commonly required to maintain different portions of the container at different temperatures, increasing the risk of refrigerant leaks and lowering the overall energy efficiency of the refrigeration system.

SUMMARY

In one embodiment, the invention provides a refrigeration system configured for use with a trailer including a container having a roof, a first sidewall, and a second sidewall. The refrigeration system includes a refrigeration unit configured to couple to the trailer and operable to condition the container. The refrigeration system also includes a duct in fluid communication between the refrigeration unit and an opening in the first sidewall. The duct is configured to direct an airflow in at least one of a first direction toward the refrigeration unit and a second direction away from the refrigeration unit.

In another embodiment, the invention provides a trailer including a container having a roof, a first sidewall, and a second sidewall. The trailer also includes a refrigeration unit operable to condition the container and a duct in fluid communication between the refrigeration unit and an opening in the first sidewall. The duct is configured to direct an airflow in at least one of a first direction toward the refrigeration unit and a second direction away from the refrigeration unit.

In yet another embodiment, the invention provides a method of conditioning a trailer. The trailer includes a container having a roof, a first sidewall, and a second sidewall. The trailer also includes a refrigeration unit. The method includes providing a first duct in fluid communication between the first refrigeration unit and an opening in the first sidewall, and a second duct in fluid communication between the refrigeration unit and an opening in the second sidewall. The method also includes directing an airflow in a first direction toward the refrigeration unit with the first duct, conditioning the container with the refrigeration unit, and directing the airflow in a second direction away from the refrigeration unit with the second duct.

Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side cross-sectional view of a trailer including a distributed refrigeration system according to an embodiment of the invention.

FIG. 2 is a top cross-sectional view of the trailer shown in FIG. 1.

FIG. 3 is a top cross-sectional view of the trailer shown in FIG. 1 including another distributed refrigeration system.

FIG. 4 is a schematic of a portion of a refrigeration unit of the distributed refrigeration systems shown in FIGS. 1 and 3.

FIG. 5 is a schematic of a portion of another refrigeration unit of the distributed refrigeration system shown in FIGS. 1 and 3.

FIG. 6 is a schematic of a transcritical closed cycle CO₂refrigeration system.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.

FIGS. 1 and 2 illustrate a trailer 10 according to an embodiment of the invention. In the illustrated embodiment, the trailer 10 includes a container 14, wheels 18 coupled to the container 14 to facilitate movement of the trailer 10, and a distributed refrigeration system 22 operable to cool the container 14. The illustrated trailer 10 is connectable to a semi-tractor (not shown) that is capable of towing the trailer 10. As shown in FIG. 1, the trailer 10 is detached from the tractor and supported on a strut 26. In other embodiments, the container 14 may be securely mounted directly to the tractor and may not be detachable.

The container 14 is configured to store cargo (e.g., food product or the like) at a reduced or refrigerated temperature. In some constructions, the container 14 may store cargo at an elevated or heated temperature. As shown in FIGS. 1 and 2, the container 14 includes a roof 30, a floor 34, a front wall 38, a rear wall 42, and opposing

sidewalls

46, 50. The illustrated trailer 10 also includes a bulkhead 54 to divide the container 14 into front and

rear portions

58, 62, or compartments. The bulkhead 54 facilitates cooling of the front and

rear portions

58, 62 to substantially different temperatures such as, for example, a chilled temperature and a frozen temperature. In the illustrated embodiment, the bulkhead 54 is retractable or collapsible so the container 14 is not always divided into the front and

rear portions

58, 62. In other embodiments, the container 14 may include two or more bulkheads to divide the container 14 into even more portions. In still other embodiments, the bulkhead 54 may be omitted entirely.

Referring to FIG. 2, the distributed refrigeration system 22 includes a first refrigeration unit 66, a second refrigeration unit 70, a first duct 74, and a second duct 78. FIG. 3 illustrates another arrangement of a distributed refrigeration system 22′ including the first and

second refrigeration units

66, 70. The

refrigeration systems

22, 22′ are considered “distributed” in that the

refrigeration units

66, 70 are spaced apart along the container 14 to facilitate uniform temperature distribution throughout the container 14. In some embodiments, the

distributed refrigeration systems

22, 22′ may include three or more refrigeration units depending on the size of the container 14, the desired temperature distribution, and/or the number of bulkheads 54. Additionally or alternatively, in other embodiments, the relative positions of the

refrigeration units

66, 70 along the container 14 may be changed.

The illustrated

refrigeration units

66, 70 are vapor compression units operable to condition (e.g., cool or heat) the container 14. Referring to FIG. 1, the first and

second refrigeration units

66, 70 are coupled (e.g., bolted) to the roof 30 of the container 14 and suspended such that each

refrigeration unit

66, 70 is positioned substantially within the container 14. In the illustrated embodiment, the roof 30 is thinned and filled with vacuum insulation and the

refrigeration units

66, 70 are bolted to an inner surface of the roof 30 to provide a low profile construction. In such an arrangement, the

refrigeration units

66, 70 are unobtrusively located (i.e., positioned above cargo within the container 14), allowing loading and unloading of the cargo from the container 14 with a reduced risk of damaging or blocking the

units

66, 70, while not increasing the overall size of the trailer 10. In addition, positioning the

refrigeration units

66, 70 proximate the roof 30 of the container 14 facilitates distributing refrigerated air, and thereby maintaining a uniform temperature, throughout the container 14.

In the illustrated embodiment, the first refrigeration unit 66 is positioned within the front portion 58 of the container 14 to condition the front portion 58 to a first temperature and the second refrigeration unit 70 is positioned within the rear portion 62 to condition the rear portion 62 to a second temperature. For example, the front portion 58 may be cooled to a frozen temperature (e.g., about minus 20° F. to about 0° F.) while the rear portion 62 may be cooled to a chilled temperature (e.g., about 35° F. to 38° F.), or vice versa. In some embodiments, the first and second temperatures may be substantially the same and/or the bulkhead 54 may be opened or removed such that the entire container 14 is conditioned to one temperature. In such embodiments, the

refrigeration units

66, 70 help maintain the substantially uniform temperature distribution throughout the container 14 and reduce the load that would otherwise be applied to a single refrigeration unit.

As shown in FIG. 4, the first refrigeration unit 66 includes a compressor 82 (e.g., a hermetic compressor), a condenser unit 86, an evaporator 90 (FIG. 2), and a receiver 94. Similar to the roof 30, a casing of the refrigeration unit 66 may be filled or covered with vacuum insulation. Although only a portion of the first refrigeration unit 66 is illustrated in detail in FIG. 4 and described below, it should be readily apparent to one skilled in the art that both

refrigeration units

66, 70 include substantially the same components and operate in a substantially similar manner. In addition, for clarity, not all of the components of the refrigeration unit 66 are shown in FIG. 4.

In the illustrated embodiment, the compressor 82 and the receiver 94 are positioned substantially within the condenser unit 86 and the evaporator 90 is positioned adjacent to the condenser unit 86. Such an arrangement makes the refrigeration unit 66 a generally self-contained unit that may be easily replaced and interchanged on the trailer 10. In frozen temperature applications, the compressor 82 may be a two-stage or multi-stage compressor.

The illustrated condenser unit 86 is positioned in fluid communication between the first duct 74 and the second duct 78 such that an airflow from the first duct 74 passes through the condenser unit 86 prior to reaching the second duct 78. As shown in FIG. 4, the condenser unit 86 includes a condenser coil 98 and a plurality of condenser fans 102, or blowers, operable to force the airflow through the first duct 74 and propel the airflow over the condenser coil 98 and into the second duct 78. In some embodiments, the compressor 82 may be surrounded by an insulating material to help thermally separate the compressor 82 from the condenser coil 98.

FIG. 5 illustrates an alternative construction of a first refrigeration unit 66′. The illustrated first refrigeration unit 66′ includes substantially the same components as the first refrigeration unit 66 of FIG. 4, and like parts have been given the same reference numbers. In the embodiment of FIG. 5, the relative positions of the components are changed compared to the positions of the components shown in FIG. 4, but the refrigeration unit 66′ still functions in substantially the same manner as the refrigeration unit 66.

Referring to FIG. 2, the first duct 74 extends along a portion of the first sidewall 46 and the second duct 78 extends along a portion of the second sidewall 50. In other embodiments, the

ducts

74, 78 may extend along a larger or smaller portion of the

sidewalls

46, 50 than the amount illustrated. As shown in FIG. 1, the first and

second ducts

74, 78 are mounted proximate to the roof 30 of the container 14 such that the

ducts

74, 78 are generally aligned with the condenser units 86 of the

refrigeration units

66, 70. In some embodiments, the condenser units 86 may be positioned relatively lower or higher (e.g., by partially cutting into the roof 30) inside the container 14. In such embodiments, the

ducts

74, 78 may be positioned relatively lower or higher along the

sidewalls

46, 50 to correspond with the alternative positions of the condenser units 86. In other embodiments, both

ducts

74, 78 may extend along the same sidewall.

In the illustrated embodiment, the first and

second ducts

74, 78 each include two

duct portions

106, 110 that extend generally perpendicularly relative to the

sidewalls

46, 50. The illustrated first duct portions 106 direct the air flowing through the first duct 74 parallel to the first sidewall 46 to flow inwardly toward the

refrigeration units

66, 70. The illustrated second duct portions 110 direct the air flowing outwardly from the

refrigeration units

66, 70 to flow through the second duct 78 and parallel to the second sidewall 50. In some embodiments, the

refrigeration units

66, 70 and the

ducts

74, 78 are sized to be in direct communication without the

duct portions

106, 110. In other embodiments, the

duct portions

106, 110 may be lengthened or shortened depending upon the width of the container 14 and the size of the

refrigeration units

66, 70.

The illustrated

ducts

74, 78 and

duct portions

106, 110 are insulated (e.g., with vacuum insulation) to help inhibit heat transfer between the refrigerated air in the container 14 and the airflow in the

ducts

74, 78. In some embodiments, the

ducts

74, 78 may be separate components that are detachable from the container 14. In other embodiments, the

ducts

74, 78 may be integrally formed as a single piece with the

sidewalls

46, 50 and/or the roof 30 of the container 14.

The first sidewall 46 includes an intake opening 114 that allows fresh ambient air from the surrounding environment to enter the first duct 74. In some embodiments, the intake opening 114 may include vents (not shown) configured to help divert ambient air into the first duct 74 while the trailer 10 is moving. The second sidewall 50 includes a discharge opening 118 to discharge the airflow from the second duct 78 into the surrounding environment after it passes through the condenser units 86. In some embodiments, the discharge opening 118 may include vents (not shown) configured to substantially inhibit ambient air from entering the second duct 78 while the trailer 10 is moving. Additionally or alternatively, the intake and

discharge openings

114, 118 may be replaced by a plurality of smaller openings extending along the lengths of the

sidewalls

46, 50.

As shown in FIG. 2, the

openings

114, 118 are generally aligned with each other on the opposing

sidewalls

46, 50 near the rear wall 42. In other embodiments, the

openings

114, 118 may be staggered along the

sidewalls

46, 50 or may be positioned in substantially different locations (e.g., adjacent to or in the front wall 38). For example, one of the

openings

114, 118 could be positioned at the front of its

respective sidewall

46, 50 while the

other opening

114, 118 could be positioned at the rear of its

respective sidewall

46, 50. In still other embodiments, at least one of the

openings

114, 118 could be positioned on the roof 30 to allow venting through the roof 30. However, positioning the

openings

114, 118 along the sidewalls 46, 50 (as opposed to the roof 30) inhibits dirt, leaves, snow, or other debris from blocking the

ducts

74, 78 and, thereby, restricting airflow into and/or out of the refrigeration system 22.

In the distributed refrigeration system 22′ shown in FIG. 3, the

duct portions

106, 110 are in direct communication between the

openings

114, 118 and the

refrigeration units

66, 70. Such an arrangement reduces the amount of space used by the distributed refrigeration system 22′ and eliminates heat transfer between air in the

ducts

74, 78 and air in the container 14.

The illustrated trailer 10 also includes a power source 122 (e.g., a diesel generator, an alternator, a fuel cell, a high capacity storage battery, or the like) coupled to the container 14 to supply power to the

refrigeration units

66, 70. As shown in FIG. 1, the power source 122 may be mounted to the front wall 38 of the container 14 or alternatively to the floor 34 of the container 14. In other embodiments, the power source 122 may be mounted in still other locations on the trailer 10. In constructions where the power source 122 is a generator, a fuel tank 126 (e.g., a diesel fuel tank) is coupled to the trailer 10 to supply fuel to the generator. In constructions where the power source 122 is an alternator, the alternator can be coupled to the engine of the truck to convert energy from the engine into electricity. In some embodiments, the trailer 10 may include a provision such that the

refrigeration units

66, 70 may be plugged into a wall outlet or secondary generator that is not part of the trailer 10 when the trailer 10 is disconnected from the tractor.

In operation, air from the environment is pulled and/or directed through the intake opening 114 and into the first duct 74 (or duct portions 106). The first duct 74 directs the airflow into the condenser units 86 of the first and

second refrigeration units

66, 70. At substantially the same time, the compressor 82 of each

refrigeration unit

66, 70 compresses a gaseous refrigerant and directs the compressed refrigerant through the condenser coils 98. The condenser fans 102 direct the airflow over the condenser coils 98 to cool and condense the compressed refrigerant into a liquid refrigerant that is directed to and temporarily stored in the corresponding receivers 94. After passing over the condenser coils 102, the airflow is directed into the second duct 78 (or duct portions 110) and away from the

refrigeration units

66, 70. The air flows through the second duct 78 toward the discharge opening 118 and is discharged back into the environment.

Meanwhile, the liquid refrigerant flows out of each receiver 94 and is directed to the corresponding evaporators 90. The liquid refrigerant is forced through corresponding expansion valves (not shown) that converts the refrigerant into a two-phase fluid. The expansion valves are generally located in the evaporators 90, although the expansion valves may alternatively be positioned in the condenser units 86. The two-phase refrigerant absorbs heat from air in the container 14 being directed through the evaporators 90. The refrigerant generally leaves the evaporators 90 in a superheated condition and is routed back to the compressors 82 for recycling. The cooled air exiting each evaporator 90 is directed back into the container 14, where it will remove heat from the cargo and maintain the cargo at the desired refrigerated or freezing temperature.

In some embodiments, the

refrigeration units

66, 70 may be transcritical closed cycle CO₂refrigeration units instead of vapor compression units. FIG. 6 illustrates a transcritical closed cycle CO₂refrigeration system 130. The CO₂refrigeration system 130 operates in a similar fashion to the vapor compression units, except the vapor CO₂refrigerant is compressed to a pressure above the thermodynamic critical point of the CO₂refrigerant. Consequently, when heat is rejected in a gas cooler 134 (previously called the condenser), vapor CO₂refrigerant is cooled but does not change phase to a liquid. The cooled, high-pressure vapor CO₂refrigerant is then passed through a heat exchanger 138 and throttled by an expansion device 142 where, similar to the vapor compression units, the low-pressure vapor CO₂refrigerant changes phase to a liquid-vapor mixture and boils to a vapor in an evaporator coil 146.

Distributed refrigeration systems improve temperature distribution in trailers by spacing multiple refrigeration units throughout the trailers. As such, distributed refrigeration systems do not require air circulation systems to evenly distribute refrigerated air, decreasing power consumption by extra fans and improving the overall system efficiency. Having multiple refrigeration units within a container also increases the cooling capacity and provides redundancy if one of the refrigeration units happens to fail.

In addition, distributed refrigeration systems generally require fewer components than existing refrigeration systems. For example, the illustrated distributed

refrigeration systems

22, 22′ significantly reduce the amount of refrigerant piping and joints compared to prevailing systems, reducing the potential for refrigerant leaks. The illustrated distributed

refrigeration systems

22, 22′ may also utilize a hermetic compressor, which further reduces the potential for leaks.

Furthermore, distributed refrigeration systems typically have better thermodynamic efficiencies than secondary loop systems since the distributed refrigeration systems do not include extra heat exchangers.

Various features and advantages of the invention are set forth in the following claims.

Claims

1. A refrigeration system configured for use with a trailer including a container having a roof, a first sidewall, and a second sidewall, the refrigeration system comprising:

a refrigeration unit configured to couple to the trailer and operable to condition the container;

a first duct in fluid communication between the refrigeration unit and an opening in the first sidewall, the first duct configured to direct an airflow in a first direction toward the refrigeration unit; and

a second duct in fluid communication between the refrigeration unit and an opening in the second sidewall, the second duct configured to direct the airflow in a second direction away from the refrigeration unit.

2. The refrigeration system of claim 1, wherein the refrigeration unit includes a condenser unit, and wherein at least one of the first duct and the second duct is in fluid communication with the condenser unit.

3. The refrigeration system of claim 1, wherein the refrigeration unit is configured to couple to the roof of the container and is configured to be positioned substantially within the container.

4. The refrigeration system of claim 1, wherein the refrigeration unit is a first refrigeration unit, and further comprising a second refrigeration unit configured to couple to the trailer and operable to condition the container, and wherein each of the first duct and the second duct is also in fluid communication with the second refrigeration unit.

5. The refrigeration system of claim 1, wherein at least one of the first duct and the second duct is configured to be positioned substantially within the container.

6. The refrigeration system of claim 1, wherein the refrigeration unit is a first refrigeration unit, and further comprising:

a second refrigeration unit configured to couple to the trailer and operable to condition the container, wherein

the second duct is in fluid communication between the second refrigeration unit and the opening in the second sidewall, the second duct configured to direct an airflow in direction away from the second refrigeration unit.

7. The refrigeration system of claim 6, wherein the trailer includes a bulkhead dividing the container into a first container portion and a second container portion, and wherein the first refrigeration unit is operable to condition the first container portion and the second refrigeration unit is operable to condition the second container portion.

8. The refrigeration system of claim 1, wherein at least a portion of the duct is insulated with vacuum insulation.

9. A trailer comprising:

a container including a roof, a first sidewall, and a second sidewall;

a refrigeration unit operable to condition the container;

10. The trailer of claim 9, wherein the refrigeration unit includes a condenser unit, and wherein at least one of the first duct and the second duct is in fluid communication with the condenser unit.

11. The trailer of claim 9, wherein the refrigeration unit is coupled to the roof of the container and is positioned substantially within the container.

12. The trailer of claim 9, wherein the refrigeration unit is a first refrigeration unit, and further comprising a second refrigeration unit operable to condition the container, and wherein each of the first duct and the second duct is also in fluid communication with the second refrigeration unit.

13. The trailer of claim 9, wherein at least one of the first duct and the second duct is positioned substantially within the container.

14. The trailer of claim 9, wherein the refrigeration unit is a first refrigeration unit, and further comprising:

a second refrigeration unit operable to condition the container, wherein

15. The trailer of claim 14, wherein the trailer includes a bulkhead dividing the container into a first container portion and a second container portion, and wherein the first refrigeration unit is operable to condition the first container portion and the second refrigeration unit is operable to condition the second container portion.

16. The trailer of claim 9, wherein at least a portion of the duct is insulated with vacuum insulation.

17. A method of conditioning a trailer, the trailer including a container having a roof, a first sidewall, and a second sidewall, and a refrigeration unit, the method comprising:

directing an airflow in a first direction toward the refrigeration unit with a first duct in fluid communication between the refrigeration unit and an opening in the first sidewall;

conditioning the container with the refrigeration unit; and

directing the airflow in a second direction away from the refrigeration unit with a second duct in fluid communication between the refrigeration unit and an opening in the second sidewall.

18. The method of claim 17, wherein the refrigeration unit includes a condenser unit, and wherein directing the airflow in the first direction toward the refrigeration unit includes directing the airflow through the condenser unit.

19. The method of claim 17, wherein the refrigeration unit is a first refrigeration unit and the trailer includes a second refrigeration unit, and further comprising:

directing the airflow in the first direction toward the second refrigeration unit with the first duct,

conditioning the container with the second refrigeration unit, and

directing the airflow in the second direction away from the second refrigeration unit with the second duct.

20. The method of claim 19, wherein the trailer includes a bulkhead dividing the container into a first container portion and a second container portion, and wherein conditioning the container with the first refrigeration unit includes conditioning the first container portion with the first refrigeration unit, and wherein conditioning the container with the second refrigeration unit includes conditioning the second container portion with the second refrigeration unit.